1. Field of the Invention
The invention relates to an endless, belt-shaped tension element for a conveyor system with at least one joining point, comprising an elastomer, in particular a cross-linked and/or thermoplastic elastomer, at least one reinforcing layer and optionally at least one tension support, two ends of the at least one reinforcing layer being disposed at the at least one joining point, a conveyor system with a circulating, endless, belt-shaped tension element and a drive system actively connected to the tension element, as well as a method of manufacturing an endless, belt-shaped tension element whereby a tension element section is made from an elastomer, a reinforcing layer is placed in it or on it, after which they are joined to one another by heat treatment, as well as the use thereof.
2. The Prior Art
Belt-shaped tension elements with various different cross-sectional shapes (primarily flat or C-, O-, U-, V-, W- or T-shaped sections) are known from numerous applications, such as conveyor belts for objects or persons, hand rails for escalators and travelators or similar. Typical applications also include bands or belts which are used in many situations to transmit driving power or to transport materials, for example.
In a known manner, belt conveyors consist of a circulating endless belt, which is partially supported by pulley blocks at the two oppositely lying end regions of the belt. To date, it has been standard practice to use separate guide rollers with belt conveyors in order to prevent the belt from migrating sideways. Endless conveyor belts are usually made from a composite material combining rubber and/or plastic with woven fabric and, for reinforcing purposes, incorporate woven fabric, non-woven materials or steel inserts and, depending on the application, one or more tension supports to increase breaking strength in the direction in which they are subjected to stress. In order to make the endless belt, there must be at least one point at which the two oppositely lying ends of the belt are joined.
Hand rails are used with escalators, travelators and similar applications as safety features for conveying persons. To this end, the hand rail must provide the passenger with a secure grip and be capable of withstanding dynamic stress and environmental influences during operation without being damaged. The endless hand rails known from the prior art are joined by various possible means and are usually made from a plurality of different materials in order to meet these requirements. The hand rail surface with which the passenger comes into contact is usually made from an elastomer blend. The top of the hand rail also protects components disposed underneath from various environmental influences and must therefore be resistant to them. It is standard practice to use reinforcing layers such as woven fabrics, fabric cords, mixtures reinforced with short fibres, etc., as a means of increasing the dimensional stability of the hand rail cross section. The hand rail is expected to have as long as possible a service life.
To render it capable of absorbing longitudinal forces in its cross section, the hand rail usually contains what might be termed tension supports, which must have a defined minimum tearing resistance, including in the butt region.
Finally, the so-called anti-friction layer forms the contact surface with the hand rail guide system and for the hand rail drive system.
Tension elements are also known which are made by a plastic extrusion process.
What all these tension elements have in common is the property whereby on bending, the components disposed at the farthest distance from the neutral axis are subjected to a particularly high degree of stress.
In this connection, taking an open section with a C-shaped cross section as mentioned above, it is evident that the fabric layer at the exposed points will be subjected to a particularly high degree of stress. Stresses are known to be caused by changes in bending at different frequencies, when the bending radii may be a single digit multiple of the component height. This bending occurs when axial tension is applied. The main requirements of flexibility and dimensional stability must there be selected within very narrowly specified tolerance ranges because the component is subject to strict safety regulations.
The fact that a maximum stiffness of the component at prescribed bending radii must not exceed or fall below a specific tolerance leads to extreme states of tension and these 3-dimensionally acting forces are dissipated at the weakest point of the material join. As a rule, they are to be found wherever there are butt/splice joints, primarily in the fabric layers.
In order to make allowance for this situation, some quite complex splice constructions have been proposed in the prior art as a means of minimising points which are susceptible to damage. For example, the two ends of a fabric web are cut at an angle, overlapped in one region and then joined to one another in this overlapping region, for example bonded.